Recovery of tar acids from coal oils or tars



May 1, 1951 D. HoRNE ErAL RECOVERY OF TAR ACIDS FROM COAL OILS OR TARS Filed July 17, 1948 Patented May 1, 1951 -uN1TED STATES PATENT AOFFICE 2,550,814 RECOVERY OF TAR ACIDS FROM COAL OILS OR TARS Donald Horne,y

Herbert Frederick Bondy, land, assignors to Low tion Limited, London,.

stock corporation Robert Pattison Marshall, and

Chesterfield, Eng- Temperature Carbonisa- England, a. British joint- Application July 17,1948, Serial No. 39,326

In Great Britain July 24, 1947 L Claim.v (Cl. 26o-627) 2. sight glass I6 and provided with an inlet I1 for the carbonio acid gas and a run-off valve I8 for the'acidified or sprung cresylate.

The carbonio acid gas supplied to the column l 6A contained 20% CO2 and was passed through a compressor I9y to a storage tank 20 provided with a pressure gauge 2l at a pressure slightly above the pressure to be maintained in the column 6.

are the ineicient use of the carbon dioxide gas, y

of which only about 60% takes part in the reaction; at the end of the reaction an average of about 12% of carbonate or unreacted cresylate remains in the separated tar acids and about 4% of tar acids or unreacted cresylate in the carbonate. Thus for iinal springing or acidification a relatively large volume of mineral acid is required with a correspondingly large loss of sodium carbonate.

According to the invention, the extraction of the tar acids from the solution or cresylate is carried out at pressures of 30-35 lbs. per sq. in. The solution or cresylate produced in the washing of the coal oils or tars with caustic soda may be passed in countercurrent with gaseous carbon dioxide of a concentration of about 15-20% through towers packed with Raschig rings.

The process of the invention was carried out in apparatus as diagrammatically illustrated by Way of example in the accompanying drawing.

From a storage vessel I heated by means of steam. pipes 2 the solution or cresylate from the washing of the coal oils or tars with caustic soda was passed through a calibrated vessel 3 for measuring the rate of flow, and then through a proportion-meter pump 4 by way of a pipe 5 to the top of a column 6 whence it passed downwardly in countercurrent with carbonic acidgas passing upwardly through the column. The column 6 which was of 3" diameter, was made up in three sections 1, 8, 9, joined together with pressure-tight flanges I0. The top section 1, 1.' in length, was tted with a pressure gauge II and provided with an inlet I2 for the feed from the storage vessel I, provided with a distributor I3 to ensure an even distribution of the cresylate over the packing, and an outlet I4 for the gases passing upwardly through the column 6. The middle section 8, of the column 6, ve feet in length, was packed with Raschig rings l5. The lowermost section 9, 1' in length, was fitted with a The outlet gases from the top of the column 6 flow either through a CO2 recorder by Way of pipe line 22, or through a gas ow meter by Way of pipe line 23.

In operation the column 6 was rst adjusted to the pressure required by means of a by-pass circuit on the storage tank of the carbonic acid gas, whereby the pressure in the storage tank was maintained at about 32 lbs/sq. in. and in the column at about 30 lbs. /sq. in.

The ow of the cresylate to the top of the column 6 was controlled by the proportion-meter pump 4.

The column was operated for between one to two hours to ensure stability of operating conditions. The chemical reaction being exothermic, resulted in a heating of parts of the column. After stabilisation of the operating conditions, the volume of flow of carbonio acid gas was slowly reduced until the exit gasesr contained from 1 to 2% CO2. After the lapse of a yperiod for conditions to become settled, samples of the tar acids and sodium carbonate were removed from the bottom of the column.

Tests on the tar acids'and carbonate solution produced were carried out as follows:

To cc. of a 50% brown oil of vitriol solution were added 50 cc. of the tar acids and intimately admixed in a stoppered vessel. After separation into two layers, the increase in volume of the mineral acid layer multiplied by two, will give an indication as to the percentage carbonate in the tar acids.

50 cc. of carbonate solution were acidified in a, standard tar acid flask, with brown oil of vitriol to which was added 5 cc. of tar acids to assist in the separation of the tar acids from the acidified carbonate. The volume of tar acids in cc. less the five cc. of tar acids added, and the result multiplied by two, will give an indication of the percentage tar acids in the carbonate.

The results obtained during three runs are tabulated below:

Press in Temp. of Rate of Per cent Per cent Gas T. A. in Carb. in Exp. Column, Inlet Feed, C02 in CO2 in throughput, Carb lbs/sq. in. Cresyl., C. oc./min. inlet gas outlet c. t./hr. Per cent Per cent l Atmos. 24 100 20 8 27 4. 8 16 2 30 25 100 20 2 31 2 2 3 35 30 100 20 1. 5 30 2 3 the results of the first experiment carried out at atmospheric pressure and the second and third experiments carried out according to the processv of the invention at pressures in the operating column respectively of 30 lbs/sq. in and 35 lbs/sq. in.

We claim:

A continuous process for the recovery of tar acids from coal tars, which comprises the following sequential steps: reacting coal tar with an aqueous solution of sodium hydroxide to form an aqueous solution of the sodium salt of the tar acids; separating said aqueous solution :from the remainder of the tar; introducing said aqueous solution into one end of an extraction zone; introducing a gas mixture containing not more than 20% of carbon dioxide into the other end of said zone; passing said mixture and said solution through said zone in countercurrent flow,

4 whereby free tar' acids are liberated, While maintaining the pressure in said zone within the range of 30-35 lbs. per sq. in.; withdrawing from said other end of said zone the resulting mixture of free acids and aqueous solution of sodium carbonate; and separating said free acids from said carbonate solution.

DONALD HORNE. ROBERT PATTISON MARSHALL. HERBERT FREDERICK BONDY.

' REFERENCES' CITED The following references are of record in the 131e' of this patent:

UNITED sTATEs PMEiWrsU4v Number Name Date 1,409,588 Runge Mar. 14,1922 1,826,369 Y Schoenburg et al. Oct. 6, 1931 20 1,956,597 Shaw May 1, 1934 2,150,656 Lounsbury Mar. 14, 1939 

